N
a metal pin made by bending double a wire, often of hemispherical section, so that it can be passed through a hole in a nut, shaft, etc, to secure another part by bending back the ends of the wire 开口销
The focus recently has been on trying to pin down the details of the neutrino's split personality: How far it travels before it changes from one type into another, and which types change into which and with what frequency.